GQZ Technology Knowledge: Analysis of Factors Effecting Sealing Performance of Sealed Deep Groove Ball Bearings

Hot tags: deep groove ball bearings (1)

Main countermeasures and measures for improving the performance of sealed deep groove ball bearings 

Abstract: through the experimental study of sealed deep groove ball bearings, the main factors affecting the sealing performance of sealed deep groove ball bearings are systematically analyzed, and the main countermeasures and measures to improve the performance of sealed deep groove ball bearings are put forward.

Key words: deep groove ball bearing; Sealed bearing; Structure; spare parts; performance

 

In order to simplify the host structure, facilitate installation, maintenance and eliminate the pollution of the surrounding environment to the bearings, various household appliances, automobiles, motorcycles, aerospace and other industries need to select a large number of sealed bearings. The quality requirements of sealed bearings must not only ensure high life reliability, but also ensure effective lubrication and sealing effects, vibration and noise reduction and other performance. This paper takes sealed deep groove ball bearing as an example for analysis.



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1 Effect of structure on sealing performance

The structure of inner ring straight bench sealed deep groove ball bearing is simple to process, and it is generally used for miniature bearings. However, its sealing performance is sensitive to the processing accuracy of bearing parts and the quality of sealing rings, and its dust-proof and grease leakage performance is general.

 

Compared with grooved inner ring deep groove ball bearing and non grooved inner ring deep groove ball bearing, the sealing performance of grooved inner ring deep groove ball bearing is superior. Compared with the grooved inner ring, the grooved inner ring lengthens the sealing radius. No matter the leakage of grease inside the bearing or the entry of dust outside the bearing, it must pass through a longer sealing radius, so it can effectively improve the sealing performance. However, from the point of view of processing and manufacturing, the inner ring has a groove sealing form, and the inner ring sealing groove needs to be processed, which increases the processing difficulty, requires higher processing accuracy of the bearing, and increases the manufacturing cost of the bearing. The inner ring non grooved sealed deep groove ball bearing is easy to manufacture and has fewer processing procedures. However, if the processing accuracy is guaranteed, it can also achieve better sealing performance.

 

Whether the inner ring is grooved or the inner ring is grooved, the sealing performance of the inner diameter lip double lip type of the sealing ring is better than that of the single lip type. The double lip type structure is composed of two front and rear contact lip edges (or two sealing gaps) and a space grease groove. The double lips play a double protective role. The grease groove between the two lips and the inner ring form a pressure buffer chamber and a grease storage chamber, which can block grease leakage, Grease leaked from the bearing cavity or dust and impurities immersed in the bearing are stored in the ring groove to form a grease ring, which increases the sealing effect.

 

2 Sealing clearance and interference

The structural form of the sealed bearing lays the foundation for the performance of the sealed bearing, and the control of the sealing clearance or interference between the inner diameter of the sealing ring and the outer diameter of the bearing inner ring is another important factor affecting the sealing performance of the sealed bearing.

 

During the test, it was found that a group of 6205- 2RZ and a group of 6206- 2RZ non-contact sealed deep groove ball bearings selected the sealing clearance according to the optimal design, and the dust-proof and grease leakage performance was unstable. Compress the seal clearance to half of the original design, and the test results are satisfactory. This fully proves that, on the premise of ensuring good coaxiality between the seal ring and the inner diameter of the bearing, the sealing performance will be significantly improved if the sealing clearance is properly compressed.

 

For contact sealed deep groove ball bearings, the interference shall be properly selected. The proper selection of interference can not only ensure good sealing effect, but also avoid excessive friction torque and high bearing temperature rise. The interference of one group of bearings is too large. The outer ring of the bearing can hardly rotate by hand. It vibrates on the vibrator. The belt of the vibrator slips due to large friction torque. During the temperature rise test, the temperature rise reached 62~ 65 e (for contact sealed deep groove ball bearings, the temperature rise test standard: temperature rise [55 E); during the grease leakage test, under the action of excessive friction, the sealing ring was dragged by the inner ring of the bearing and rotated with the inner ring, and the grease leaked from the outer diameter of the sealing ring and the sealing groove of the outer ring of the bearing, resulting in poor sealing performance.

 

3 Control of bearing machining accuracy

The processing of sealed deep groove ball bearings is much more complicated than that of ordinary deep groove ball bearings, and many processes are added. In the process of machining, in addition to the quality control of general deep groove ball bearings, the dimensional accuracy, shape and position accuracy, inner ring outer chamfer, bearing inner and outer ring groove position and groove to end face parallelism (groove pendulum) control should also be increased.

 

The outer ring sealing groove is used to fix the sealing ring, and the inner ring sealing groove is used to ensure the sealing clearance or interference. Therefore, its dimensional accuracy and shape and position accuracy directly affect the sealing performance of the finished bearing. If the strict control of the size and shape and position accuracy of the seal groove is neglected in the machining stage, the processing width and depth of the seal groove are different, the roundness and coaxiality errors are too large, the inner and outer ring seal grooves are axially misaligned, the seal groove is not in the same plane, or the ferrule is seriously deformed during heat treatment. After the bearing is assembled, the seal ring rotates due to poor positioning, some seal clearances are too large and some are too small, and axial movement occurs during the bearing operation, Will seriously affect the sealing performance of sealed bearings.

 

The outer chamfer size of the bearing inner ring also has a great influence on the sealing performance. The outer diameter (or groove) of the bearing inner ring is matched with the inner diameter lip of the sealing ring to ensure the sealing effect. Generally, the lip of the sealing ring is narrow, and the outer chamfer of the bearing inner ring is small. If the chamfer size is large, the axial sealing size will be reduced, the outer lip of the sealing ring will not play a sealing role, and the sealing effect will be affected. Therefore, the outer chamfer size of the inner ring should be strictly controlled.

 

Some sealed deep groove ball bearings were found to be black after the test, so the amount of dust invasion could not be checked under the microscope, and there was not much dust. After analysis, it was found that the processing quality of cage or sealing groove was a problem. The cage of sealed deep groove ball bearing is generally guided by the rolling element. If the machining accuracy of the cage does not meet the requirements, the bearing may be backed up during operation. Some small sealed deep groove ball bearings are easy to collide with the inner ring due to small size, processing error of cage and other factors, and the wear of backup sleeve is obvious. In the test, it is shown that the vibration is large, the noise is large, the temperature rises, and the local high heat caused by the wear of backup sleeve leads to the failure and blackening of lubricating grease. In some cases, the processing error of the seal groove of the ferrule is large. The pocket hole of the cage is higher than the end face of the seal groove of the ferrule. The cage is in contact with the seal ring. When the bearing is running, the cage and the seal ring rub against each other, resulting in the deformation and wear of the seal ring. At the same time, the local high temperature of the friction makes the grease black and invalid.

 

The control of the inner and outer ring groove position and the parallelism of the groove to the end face (groove swing) of the sealed deep groove ball bearing directly affects the sealing performance of the sealed deep groove ball bearing. If not strictly controlled, the inner and outer ring seal grooves will be misaligned, especially the non datum seal grooves. The groove swing is the main reason for the side swing of the end face of the finished product. If it is too large, the bearing is prone to axial movement during operation, This will affect the sealing performance of the bearing.

 

4 Rubber sealing ring

The structure, material and processing accuracy of the rubber seal ring with large amount in the sealed deep groove ball bearing have a great impact on the sealing performance of the sealed deep groove ball bearing. The sealing ring material shall be selected according to different working conditions and different environmental media of the bearing in use. The seal ring framework shall have good rigidity, uniform material, antirust treatment on the surface, and dimensional accuracy. The rubber shall be uniform, the physical properties shall meet the requirements, have a certain hardness and elasticity, match with the lubricating grease and antirust oil, and firmly adhere to the framework. The structural shape and dimensional accuracy of the finished sealing ring shall meet the requirements.

 

The main problems found in the test are: (1) the coaxiality error of the inner and outer diameter of the sealing ring is large, the inner diameter of the sealing ring is oval, the sealing clearance with the bearing is uneven after assembly, and the sealing performance is not good. (2) some sealing ring lips have good elasticity and some have poor elasticity. (3) the lip of the sealing ring has large burrs and the lip is uneven; The lip is defective, and part of the lip is cut off during film cutting. (4) the rigidity of the framework is not enough, and the sealing ring is warped and deformed. (5) The appearance of the sealing ring is not good, and the glue overflow on the parting surface is not repaired. (6) the sealing ring is stored for a long time, and the rubber is aged and deformed.

 

Because the internal pressure and temperature of the bearing are greater than the external pressure and temperature during the use of the bearing, and the sealing ring, especially the lip, has to bear greater pressure, the dimensional accuracy and physical performance of the sealing ring are directly related to the sealing performance of the sealed deep groove ball bearing.

 

5 Grease

The important function of grease in sealed deep groove ball bearing is to ensure that the sealed deep groove ball bearing has sufficient lubrication, and to ensure the life reliability and stable sealing performance of the bearing. The lubricating grease shall be selected according to the use, application occasion and service conditions of the bearing. The general requirements are as follows: good stability and fluidity, good temperature characteristics, good vibration and noise reduction, good cleanliness, good rust prevention, water and moisture resistance, good adaptability to the rubber used for sealing ring, good dust and leakage resistance, etc.

 

From the perspective of improving the sealing performance of sealed deep groove ball bearings, sealed deep groove ball bearings should choose lubricating grease with high viscosity, which has poor fluidity, is not easy to expose, and has good sealing, dust-proof and leak proof performance. However, if the viscosity of the grease is too high, the mixing resistance of the grease is large during the bearing operation, and the temperature rise of the sealed deep groove ball bearing increases, the fluidity of the grease increases, and the grease is easy to leak. Therefore, when selecting lubricating grease, the service conditions and working conditions of sealed deep groove ball bearings should be fully considered to ensure the service life reliability and sealing performance requirements of sealed deep groove ball bearings.

 

6 Effect of working conditions on sealing performance

Generally, the rotating speed of the sealed bearing has little effect on the dust-proof and grease leakage performance. However, if there is a large amount of grease filling, the grease leakage will increase with the increase of rotating speed after the bearing is saturated, and the external dust will invade the bearing more with the increase of grease leakage. The rotating speed has a great influence on the temperature rise. As the rotating speed increases, the rolling friction of all parts of the bearing increases, and the temperature of the bearing also increases.

 

Radial load has little effect on sealing performance. However, if the bearing is improperly installed and bears axial load in use, it will affect the sealing performance. In particular, the inner ring grooveless seal deep groove ball bearing bears a great impact. When the inner ring grooveless structure bears axial load, the bearing inner ring, outer ring and sealing ring will have axial displacement, and the size of the sealing part will be reduced, resulting in the reduction of sealing performance. The radial load is larger and the temperature rise increases, but the influence of load on temperature rise is less than that of rotating speed.

 

For sealed bearings with the same working conditions, the sealing performance of the bearing decreases slightly due to high ambient temperature. When the ambient temperature is high, the viscosity of the grease decreases and the fluidity increases, which is easy to cause leakage, and more dust invades the interior of the bearing. The temperature rise is a comprehensive reflection of the heat generated by the bearing during operation and the heat exchange with the surrounding environment. If the ambient temperature is high and the heat exchange is unfavorable, the temperature rise of the bearing will be high.

 

More about GQZ Deep Groove Ball Bearings:

GQZ Deep groove ball bearings are the most widely used bearing type and are extremely versatile. This bearing features low friction, optimized for low noise and vibration, enabling high rotational speeds. They accommodate radial and axial loads in both directions, are easy to install and require less maintenance than other types of bearings.

 

Deep groove ball bearings are the most commonly used rolling bearings. It has a simple structure and is easy to use. It is mainly used to bear radial load, but when the radial clearance of the bearing is increased, it has a certain performance of angular contact ball bearing and can bear combined radial and axial loads. It can also be used to bear pure axial load when the rotational speed is high and the thrust ball bearing is not suitable. Compared with other types of bearings with the same size and size as deep groove ball bearings, this type of bearing has a small friction coefficient and a high limit speed. However, it is not resistant to impact and is not suitable for bearing heavy loads.


Deep groove ball bearing 


After the deep groove ball bearing is mounted on the shaft, within the axial clearance range of the bearing, the axial displacement of the shaft or the housing can be limited in two directions, so it can be axially positioned in both directions. In addition, this type of bearing also has a certain self-aligning ability. When it is inclined 2' to 10' relative to the housing hole, it can still work normally, but it has a certain impact on the bearing life.

 

 


2022-06-29